The experiments described in this proposal are designed to explore functional characteristics of developing kidney under physiological and pathological conditions. Preliminary investigations performed by micropuncture techniques have shown that the increase in pressure for ultrafiltration (PUF) plays a relatively small role in the 25 fold increase in glomerular filtration rate (GFR) which occurs between childhood and adulthood, in a variety of animal species. Studies are being conducted to characterize the other two variables, namely changes in the permeability characteristics and surface area of the glomerular capillary. Clearance of dextrans with diameters varying between 18 and 50 Angstrom units are being used to assess the former and a new method, based on neutron activation of the rubber compound injected into the renal vasculature of the kidney fixed in vivo, has been used to assess the latter variable in maturing dogs. These studies will allow us to quantify the contribution of each of the factors involved in the process of glomerular filtration to the overall rise observed during development. Ureteral obstruction is one of the most common congenital abnormalities of the urinary tract in children and is responsible for an appreciable number of patients with end stage renal disease. The effects of chronic partial unilateral obstruction on discreet aspects of renal function is being assessed in guinea pigs at various stages of postnatal development. Lead intoxication is still of epidemic proportions among children in deprived areas of the large cities. Its impact upon the kidney has been investigated in an animal model which mimics the conditions encountered in life. The objective of this study was to determine whether exposure to this noxious agent for a limited period during growth can result in complications encountered much later in life.